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Andrea Trost, Falk Schroedl, Barbara Bogner, Clemens A. Strohmaier, Christian W. Runge, Herwig Brandtner, Guenther Grabner, Ludwig Aigner, Herbert A. Reitsamer; Comparative Characterization of Choroidal and Retinal Pericytes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6036.
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Pericytes, cells closely adjacent to blood vessels, are important for vascular development, stabilization and remodeling. They potentially influence vascular diameter. In pathologic conditions (e.g., diabetes, hypertension, neovascularization) a change in pericyte coverage of microvessels is found, suggesting a possible key role of pericytes in the pathogenesis of various blood flow related diseases. However, the function of pericytes in these ocular circuits is not completely understood. In the present study, we present a thorough characterization of retinal and choroidal pericytes as a basis for pending functional studies.
Using immunohistochemistry, cultivated bovine retinal and choroidal pericytes were tested for the pericyte markers NG2, CD146, PDGFRb, α-SMA. To distinguish pericytes from endothelial cells in vitro as well as in retinal and choroidal cryosections, a screening for the endothelial cell markers CD31 and lectin1 was performed. Additionally, real-time PCR was used to identify pericyte and endothelial marker expression on the mRNA level.
Immunohistochemistry revealed a co-localization of the pericyte markers NG2 and CD146/PDGFRb in tissue slices and cultivated retinal and choroidal perivascular cells. All cultivated pericytes were α-SMA-positive, whereas in cryosections only pericytes surrounding vessels >10µm showed immunoreactivity for α-SMA. The endothelium specific marker lectin1 was co-localized with NG2, CD146 and α-SMA. On mRNA expression level NG2 was expressed by pericytes only, while CD146 and α-SMA were also detectable in endothelial cells.
Although data on pericyte characterization have been released, no distinct pericyte marker is defined up to now. Pericyte markers tested here partly showed an overlap with endothelial markers and vice versa. Our study highlights the challenge to find an explicit pericyte marker and also the importance to differentiate between pericytes and endothelial cells independently of their characteristic position in and around vessels. Additional characterization studies are currently performed to unveil a proper marker combination in order to definitely identify pericytes as a basis for functional studies.
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